THE MONTEREGIAN HILLS 



265 



For the analysis of the Mount Johnson essexite (No. i) as well 

 as for- that of the associated pulaskite, which is given below, I 

 am indebted to Professor Norton- Evans, while the analysis of 

 the olivine-bearing variety of the essexite (No. 2) was made for 

 me by Mr. M. F. Connor. The methods recommended by 

 Hillebrand and employed in the very accurate, analytical work 

 carried out in the laboratory of the United States Geological 

 Survey were followed by both analysts and every precaution 

 was taken to insure accuracy. 



Ill 



IV 



VI 



SiO, 



TiOs 



AI2U3 



Fe^03 



FeO 



NiO + CoO 



MnO 



MgO 



CaO 



BaO 



Na^O 



K2O 



PA 



CI 



H^O 



48.85 

 2.47 



19.38 

 4.29 

 4.94 

 not det. 

 0. 19 

 2.00 

 7.98 



5-44 

 1. 91 

 1.23 

 not det. 

 0.68 



48.69 

 2.71 



17.91 

 3-09 

 6.41 

 0.05 

 0.15 

 3.06 

 7.30 

 0.08 



5-95 

 2.56 

 I . II 

 not det. 

 0.95 



53-15 



. 1-52 



17.64 



3. 10 



4.65 

 not det. 

 0.46 

 2.94 

 5-66 

 0.13 

 5.00 

 3. 10 

 0.65 

 0.07 

 1 . 10 



Total 99.36 



100.02 



99.84 



46.99 

 2.92 



17.94 

 2.56 

 7.56 

 not det. 

 [race 

 3.22 



7-85 

 none 



6.35 

 2.62 

 0.94 



0.65 



47.67 



99.60 



100.15 



82 



50.40 

 1. 17 



[ 5-58 



not det. 

 0.77 



6.77 



6.24 

 2.56 

 0.09 



I. Normal essexite (andose), Mount Johnson, Quebec. 



II. Olivine-bearing essexite (essexose), Mount Johnson, Quebec. 



III. Essexite (akerose), Shefford mountain, Quebec, {^Americatt Geologist, 

 igoi, p. 201), (with CO2O.39 and SO3O.28). 



IV. Essexite (essexose), Salem Neck, Salem, Mass. (Washington, Jour. 

 Geol., 1899, p. 57). 



V. Theralite, Elbow Creek, Crazy mountains, Montana. 



VI. Rock forming transition from essexite to pulaskite. Mount Johnson, 

 Quebec. (Partial analysis. The iron present is all calculated as FeO.) 



The analyses (Nos. i and 2) of the two varieties of the 

 essexite from Mount Johnson can be readily calculated out so as 

 to show the quantitative mineralogical composition of the rocks. 



The calculation of the vwde'' — or relative proportion of the 



minerals actually present gives the following result: 



^ Quantitative Classificatio7i of Igneous Rocks (C /. P, W.) (University of Chicago 

 Press, 1903), p. 147. 



